This study is directed at expanding our understanding of factors responsible for the doubling in risk of low birthweight (LBW) infants among blacks vs whites, and the excess in LBW among blacks compared with another major minority groups, Hispanics. The source of information is the public use data tapes prepared in the National Longitudinal Surveys of labor Market Experience of Youth (NSLY) of the Center For Human Resources Research (CHRR), Ohio State University. The data are derived from personal interviews, 1979-1986 with a cohort of non-institutionalized young women and men aged 14-21 years as of January 1979. The data files include variables for the mothers of the 5,500 children in the sample that are highly relevant for investigations of risk factors for low birth weight and prematurity but which have been incompletely studied. An important aspect of the study is the application of models suitable for longitudinal analyses. Specific aims follow: 1. To explore the degree to which racial differences in low birthweight are accounted for by differences in major social, biologic, and behavioral characteristics. 2. To compare the contributions of major social, biologic and other variables to shortened gestation and to retarded fetal growth among low birthweight infants who are black, which, or Hispanic. 3. To investigate similarities and differentials among different racial and ethnic groups on the extent to which there is consistency in low birthweight when underlying major risk factors are unchanged across successive pregnancies and conversely, the extent to which low birthweight differs when major risk factors change from one pregnancy to the next.